U.S. patent application number 16/704262 was filed with the patent office on 2020-06-25 for communications device and method for operating a communications device.
The applicant listed for this patent is NXP B,V.. Invention is credited to Steve Charpentier, Stefan Mendel, ULRICH ANDREAS MUEHLMANN.
Application Number | 20200204427 16/704262 |
Document ID | / |
Family ID | 65278160 |
Filed Date | 2020-06-25 |
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United States Patent
Application |
20200204427 |
Kind Code |
A1 |
MUEHLMANN; ULRICH ANDREAS ;
et al. |
June 25, 2020 |
COMMUNICATIONS DEVICE AND METHOD FOR OPERATING A COMMUNICATIONS
DEVICE
Abstract
Embodiments of communications devices and methods for operating
a communications device are described. In an embodiment, a
communications device includes a complex multiplier configured to
multiply a first input complex signal with a second input complex
signal to generate an output complex signal, an amplifier
configured to amplify an imaginary part of the output complex
signal to generate an amplification result, a delay element
configured to delay a rotation angle signal that is related to the
second input complex signal, and a subtractor configured to
subtract the amplification result from the delayed rotation angle
signal to generate the rotation angle signal. Other embodiments are
also described.
Inventors: |
MUEHLMANN; ULRICH ANDREAS;
(Graz, AT) ; Mendel; Stefan; (Graz, AT) ;
Charpentier; Steve; (Antibes, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NXP B,V. |
Eindhoven |
|
NL |
|
|
Family ID: |
65278160 |
Appl. No.: |
16/704262 |
Filed: |
December 5, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 27/0014 20130101;
H03D 7/165 20130101; H04L 27/362 20130101; H03F 3/19 20130101; H04L
27/38 20130101; H03D 2200/0082 20130101; H04B 1/10 20130101; H03D
2200/0072 20130101 |
International
Class: |
H04L 27/36 20060101
H04L027/36; H04L 27/38 20060101 H04L027/38 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2018 |
EP |
18306748.7 |
Claims
1. A communications device, the communications device comprising: a
complex multiplier configured to multiply a first input complex
signal with a second input complex signal to generate an output
complex signal; an amplifier configured to amplify an imaginary
part of the output complex signal to generate an amplification
result; a delay element configured to delay a rotation angle signal
that is related to the second input complex signal; and a
subtractor configured to subtract the amplification result from the
delayed rotation angle signal to generate the rotation angle
signal.
2. The communications device of claim 1, wherein the first input
complex signal comprises a real part that is a baseband in-phase
(I) component and an imaginary part that is a baseband quadrature
(Q) component.
3. The communications device of claim 2, further comprising a
baseband IQ demodulator configured to generate the baseband
in-phase (I) and quadrature (Q) components based on a radio
frequency (RF) input signal.
4. The communications device of claim 3, wherein the baseband IQ
demodulator comprises a clock source configured to generate a clock
signal, and wherein the baseband IQ demodulator is configured to
generate the baseband in-phase (I) and quadrature (Q) components
based on the RF input signal and the clock signal.
5. The communications device of claim 1, wherein the second input
complex signal is represented as: cos(phi(j))+1i*sin(phi(j)), where
phi is the rotation angle signal, and where j is complex unit.
6. The communications device of claim 1, wherein the complex
multiplier is configured to output a real part of the output
complex signal for decoding.
7. The communications device of claim 1, further comprising a
decoder configured to decode a real part of the output complex
signal.
8. The communications device of claim 1, wherein the amplifier is
configured to amplify the imaginary part of the output complex
signal by an amplification gain.
9. A method for operating a communications device, the method
comprising: multiplying a first input complex signal with a second
input complex signal to generate an output complex signal;
amplifying an imaginary part of the output complex signal to
generate an amplification result; delaying a rotation angle signal
that is related to the second input complex signal; and subtracting
the amplification result from the delayed rotation angle signal to
generate the rotation angle signal.
10. The method of claim 9, wherein the first input complex signal
comprises a real part that is a baseband in-phase (I) component and
an imaginary part that is a baseband quadrature (Q) component.
11. The method of claim 10, further comprising generating the
baseband in-phase (I) and quadrature (Q) components based on a
radio frequency (RF) input signal.
12. The method of claim 11, further comprising obtaining a clock
signal, wherein generating the baseband in-phase (I) and quadrature
(Q) components based on the RF input signal comprises generating
the baseband in-phase (I) and quadrature (Q) components based on
the RF input signal and the clock signal.
13. The method of claim 9, wherein the second input complex signal
is represented as: cos(phi(j))+1i*sin(phi(j)), where phi is the
rotation angle signal, and where j is complex unit.
14. The method of claim 9, further comprising outputting a real
part of the output complex signal for decoding.
15. The method of claim 9, further comprising decoding a real part
of the output complex signal.
Description
BACKGROUND
[0001] Communications devices that communicate with each other
wirelessly can be affected by materials used in the communications
devices and/or environmental factors. For example, many wireless
communications devices (e.g., mobile devices) are encapsulated in
metal enclosures, which can affect magnetic field distributions.
Consequently, communications performance may degrade in corner
cases (e.g., when a wireless communications device is too close to
a corresponding wireless communications device or is too far away
from a corresponding wireless communications device). For example,
parasitic phase modulation may be introduced, which can cause loss
of phase information and/or loss of magnitude gradient and
therefore can impact the accuracy of a recovered clock signal.
Inaccurate clock signal recovery can negatively impact data
reception.
SUMMARY
[0002] Embodiments of communications devices and methods for
operating a communications device are described. In an embodiment,
a communications device includes a complex multiplier configured to
multiply a first input complex signal with a second input complex
signal to generate an output complex signal, an amplifier
configured to amplify an imaginary part of the output complex
signal to generate an amplification result, a delay element
configured to delay a rotation angle signal that is related to the
second input complex signal, and a subtractor configured to
subtract the amplification result from the delayed rotation angle
signal to generate the rotation angle signal. Other embodiments are
also described. In an embodiment, the first input complex signal
includes a real part that is a baseband in-phase (I) component and
an imaginary part that is a baseband quadrature (Q) component. In
an embodiment, the communications device further includes a
baseband IQ demodulator configured to generate the baseband
in-phase (I) and quadrature (Q) components based on a radio
frequency (RF) input signal.
[0003] In an embodiment, the baseband IQ demodulator includes a
clock source configured to generate a clock signal, and wherein the
baseband IQ demodulator is configured to generate the baseband
in-phase (I) and quadrature (Q) components based on the RF input
signal and the clock signal.
[0004] In an embodiment, wherein the second input complex signal is
represented as:
cos(phi(j))+1i*sin(phi(j)),
where phi is the rotation angle signal, and where j is complex
unit.
[0005] In an embodiment, the complex multiplier is configured to
output a real part of the output complex signal for decoding.
[0006] In an embodiment, the communications device further includes
a decoder configured to decode a real part of the output complex
signal.
[0007] In an embodiment, the amplifier is configured to amplify the
imaginary part of the output complex signal by an amplification
gain.
[0008] In an embodiment, a communications device includes a
baseband IQ demodulator configured to generate baseband in-phase
(I) and quadrature (Q) components based on a radio frequency (RF)
input signal and a phase rotator connected to the baseband IQ
demodulator. The phase rotator includes a complex multiplier
configured to multiply a first input complex signal with a second
input complex signal to generate an output complex signal, where
the first input complex signal comprises a real part that is the
baseband in-phase (I) component and an imaginary part that is the
baseband quadrature (Q) component, and where the complex multiplier
is configured to output a real part of the output complex signal
for decoding, an amplifier configured to amplify an imaginary part
of the output complex signal to generate an amplification result, a
delay element configured to delay a rotation angle signal that is
related to the second input complex signal, and a subtractor
configured to subtract the amplification result from the delayed
rotation angle signal to generate the rotation angle signal.
[0009] In an embodiment, the baseband IQ demodulator includes a
clock source configured to generate a clock signal, and wherein the
baseband IQ demodulator is configured to generate the baseband
in-phase (I) and quadrature (Q) components based on the RF input
signal and the clock signal.
[0010] In an embodiment, the second input complex signal is
represented as:
cos(phi(j))+1i*sin(phi(j)),
where phi is the rotation angle signal, and where j is complex
unit.
[0011] In an embodiment, the communications device further includes
a decoder configured to decode the real part of the output complex
signal.
[0012] In an embodiment, a method for operating a communications
device involves multiplying a first input complex signal with a
second input complex signal to generate an output complex signal,
amplifying an imaginary part of the output complex signal to
generate an amplification result, delaying a rotation angle signal
that is related to the second input complex signal, and subtracting
the amplification result from the delayed rotation angle signal to
generate the rotation angle signal.
[0013] In an embodiment, the first input complex signal includes a
real part that is a baseband in-phase (I) component and an
imaginary part that is a baseband quadrature (Q) component.
[0014] In an embodiment, the method further involves generating the
baseband in-phase (I) and quadrature (Q) components based on a
radio frequency (RF) input signal.
[0015] In an embodiment, the method further involves obtaining a
clock signal, wherein generating the baseband in-phase (I) and
quadrature (Q) components based on the RF input signal comprises
generating the baseband in-phase (I) and quadrature (Q) components
based on the RF input signal and the clock signal.
[0016] In an embodiment, the second input complex signal is
represented as:
cos(phi(j))+1i*sin(phi(j)),
where phi is the rotation angle signal, and where j is complex
unit.
[0017] In an embodiment, the method further involves outputting a
real part of the output complex signal for decoding.
[0018] In an embodiment, the method further involves decoding a
real part of the output complex signal.
[0019] In an embodiment, amplifying the imaginary part of the
output complex signal involves amplifying the imaginary part of the
output complex signal by an amplification gain.
[0020] Other aspects and advantages of embodiments of the present
invention will become apparent from the following detailed
description, taken in conjunction with the accompanying drawings,
depicted by way of example of the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 depicts an embodiment of a communications device that
can be used with a counterpart communications device to form a
communications system.
[0022] FIG. 2 depicts an embodiment of a receiver unit, which may
be an embodiment of an RF transceiver of the communications device
and/or an RF transceiver of the counterpart communications device
depicted in FIG. 1.
[0023] FIG. 3 is a plot of the real part and the imaginary part of
an output complex signal of a complex multiplier of a phase rotator
as depicted in FIG. 2 and a rotation angle signal in an example
operation of the phase rotator.
[0024] FIG. 4 depicts another embodiment of a receiver unit, which
may be an embodiment of an RF transceiver of the communications
device and/or an RF transceiver of the counterpart communications
device depicted in FIG. 1.
[0025] FIG. 5 is a process flow diagram of a method for operating a
communications device in accordance with an embodiment of the
invention.
[0026] Throughout the description, similar reference numbers may be
used to identify similar elements.
DETAILED DESCRIPTION
[0027] It will be readily understood that the components of the
embodiments as generally described herein and illustrated in the
appended figures could be arranged and designed in a wide variety
of different configurations. Thus, the following detailed
description of various embodiments, as represented in the figures,
is not intended to limit the scope of the present disclosure but is
merely representative of various embodiments. While the various
aspects of the embodiments are presented in drawings, the drawings
are not necessarily drawn to scale unless specifically
indicated.
[0028] The described embodiments are to be considered in all
respects only as illustrative and not restrictive. The scope of the
invention is, therefore, indicated by the appended claims rather
than by this detailed description. All changes which come within
the meaning and range of equivalency of the claims are to be
embraced within their scope.
[0029] Reference throughout this specification to features,
advantages, or similar language does not imply that all of the
features and advantages that may be realized with the present
invention should be or are in any single embodiment. Rather,
language referring to the features and advantages is understood to
mean that a specific feature, advantage, or characteristic
described in connection with an embodiment is included in at least
one embodiment. Thus, discussions of the features and advantages,
and similar language, throughout this specification may, but do not
necessarily, refer to the same embodiment.
[0030] Furthermore, the described features, advantages, and
characteristics of the invention may be combined in any suitable
manner in one or more embodiments. One skilled in the relevant art
will recognize, in light of the description herein, that the
invention can be practiced without one or more of the specific
features or advantages of a particular embodiment. In other
instances, additional features and advantages may be recognized in
certain embodiments that may not be present in all embodiments of
the invention.
[0031] Reference throughout this specification to "one embodiment,"
"an embodiment," or similar language means that a particular
feature, structure, or characteristic described in connection with
the indicated embodiment is included in at least one embodiment.
Thus, the phrases "in one embodiment," "in an embodiment," and
similar language throughout this specification may, but do not
necessarily, all refer to the same embodiment.
[0032] FIG. 1 depicts an embodiment of a communications device 102
that can be used with a counterpart communications device 104 to
form a communications system 100. In the communications system
depicted in FIG. 1, the communications device 102 communicates with
the counterpart communications device 104 via a communications
channel 106. In some embodiments, the communications device 102 is
a card/transponder device or the communications device 102 is in a
"card-mode" in which the communications device 102 behaves as a
card/transponder device and the counterpart communications device
104 is a dedicated reader device or a communications device in
"reader-mode" in which the counterpart communications device 104
behaves as a reader device. In some other embodiments, the
communications device 102 is a reader device or the communications
device is in a reader mode and the counterpart communications
device 104 is a dedicated card device or a communications device in
card-mode.
[0033] In the embodiment depicted in FIG. 1, the communications
device 102 includes an antenna 112 and an RF transceiver 114
configured to receive incoming RF signals from the antenna and/or
to transmit outgoing RF signals through the antenna. The antenna
may be any suitable type of antenna. In some embodiments, the
antenna is an induction type antenna such as a loop antenna or any
other suitable type of induction type antenna. However, the antenna
is not limited at an induction type antenna. The communications
device may be fully or partially implemented as an integrated
circuit (IC) device. In some embodiments, the communications device
is a handheld computing system or a mobile computing system, such
as a mobile phone that includes one or more IC devices. Although
the illustrated communications device is shown with certain
components and described with certain functionality herein, other
embodiments of the communications device 102 may include fewer or
more components to implement the same, less, or more
functionality.
[0034] In some embodiments, the communications device 102
communicates with other communications devices (e.g., the
counterpart communications device 104) via inductive coupling. For
example, the communications device 102 is a near field
communications (NFC) device that uses magnetic field induction for
communications in close proximity. The communications device 102
can be configured for either passive load modulation (PLM) or
active load modulation (ALM). In some embodiments, the
communications device is implemented as an RF transponder that is
compatible with the International Organization for Standardization
(ISO)/the International Electrotechnical Commission (IEC) 14443
standard that may operate at 13.56 MHz. In these embodiments, the
antenna 112 is an induction type antenna such as a loop antenna or
any other suitable type of induction type antenna.
[0035] In the embodiment depicted in FIG. 1, the counterpart
communications device 104 includes an antenna 122 and an RF
transceiver 124 configured to receive incoming RF signals from the
antenna 122 and/or to transmit outgoing RF signals through the
antenna 122. The antenna may be any suitable type of antenna. In
some embodiments, the antenna is an induction type antenna such as
a loop antenna or any other suitable type of induction type
antenna. However, the antenna is not limited at an induction type
antenna. The counterpart communications device 104 may be fully or
partially implemented as an IC device. In some embodiments, the
counterpart communications device is a handheld computing system or
a mobile computing system, such as a mobile phone. Although the
illustrated counterpart communications device is shown with certain
components and described with certain functionality herein, other
embodiments of the counterpart communications device may include
fewer or more components to implement the same, less, or more
functionality.
[0036] In some embodiments, the counterpart communications device
104 communicates with other communications devices (e.g., the
communications device 102) via inductive coupling. For example, the
counterpart communications device 104 is an NFC device that uses
magnetic field induction for communications in close proximity. The
counterpart communications device can be configured for either PLM
or ALM. In some embodiments, the counterpart communications device
is implemented as an RF transponder that is compatible with the
ISO/IEC 14443 standard that may operate at 13.56 MHz. In the
embodiments, the antenna 122 is an induction type antenna such as a
loop antenna or any other suitable type of induction type
antenna.
[0037] In an example operation of the communications system 100, an
RF signal is received by the antenna 112 of the communications
device 102 from the antenna 122 of the counterpart communications
device 104 and is passed to the RF transceiver 114 of the
communications device 102 to convert the RF signal into a digital
signal, which can be further processed by a digital processor. A
signal may be generated in response to the RF signal and is used to
produce an outgoing RF signal at the RF transceiver 114, which may
be transmitted to the counterpart communications device using the
antenna 112.
[0038] FIG. 2 depicts a receiver unit 214 that is an embodiment of
the RF transceiver 114 of the communications device 102 and/or the
RF transceiver 124 of the counterpart communications device 104
depicted in FIG. 1. In the embodiment depicted in FIG. 2, the
receiver unit includes a phase rotator 220, which includes a
complex multiplier 222, an amplifier 224, a delay element 226, and
a subtractor 228. Each of the complex multiplier, the amplifier,
the delay element, and the subtractor may be implemented as
hardware, software, firmware, and/or a combination of hardware,
software, and/or firmware. In some embodiments, at least one of the
complex multiplier, the amplifier, the delay element, and the
subtractor is implemented as a processor such as a microcontroller
or a central processing unit (CPU). The receiver unit depicted in
FIG. 2 is a possible implementation of the RF transceiver 114 or
124 depicted in FIG. 1. However, the RF transceiver 114 or 124
depicted in FIG. 1 can be implemented differently from the receiver
unit depicted in FIG. 2.
[0039] Compared to a receiver that relies on a recovered clock for
data reception, the receiver unit 214 depicted in FIG. 2 does not
rely solely on a clock-recovery mechanism for data reception and
decoding. For example, the phase rotator 220 can operate with a
local clock source (e.g., a local oscillator), which is used to
generate input data for the phase rotator. Because the receiver
unit depicted in FIG. 2 does not rely solely on a clock-recovery
mechanism for data reception and decoding, parasitic phase
modulation that may be introduced based on the proximity between
the communications devices does not affect data reception and
decoding at the corresponding receiver unit.
[0040] In the embodiment depicted in FIG. 2, the complex multiplier
222 is configured to multiply an incoming complex signal (also
referred to as a first input complex signal) 230 with a second
input complex signal 232 to generate an output complex signal 234.
In some embodiments, the first input complex signal includes a real
part that is a baseband in-phase (I) component 236 and an imaginary
part that is a baseband quadrature (Q) component 238. In some
embodiments, the baseband in-phase (I) and quadrature (Q)
components are derived from an RF signal that is received by the
antenna 112 or the antenna 122. In some embodiments, the complex
multiplier is configured to output a real part of the output
complex signal for decoding.
[0041] In the embodiment depicted in FIG. 2, the complex multiplier
222, the amplifier 224, the delay element 226, and the subtractor
228 form a phase rotation loop that continuously rotates the first
input complex signal 230 to reduce the imaginary part 248 of the
output complex signal 234 such that encoded information is
predominantly carried by the real part 246 of the output complex
signal. In some embodiments, the imaginary part of the output
complex signal is changed (e.g., reduced or increased) to zero by
the phase rotation loop. For example, the imaginary part is reduced
from a positive number (e.g., 100 or other suitable number) to 0 by
the phase rotation loop. Because the information is predominantly
carried by the real part of the output complex signal, information
can be decoded from the real part of the output complex signal by a
digital signal processor (e.g., using decoding and bit-slicing
operations to form the logical representations of true and false),
thereby reducing or even eliminating the need to decode the
imaginary part of the output complex signal to recover the carried
information. Consequently, a separate decoder is not needed to
decode the imaginary part of the output complex signal.
Additionally, a separate/parallel decoding and bit-slicing chain is
not needed within a digital decoder to decode the real part of the
output complex signal.
[0042] In the embodiment depicted in FIG. 2, the amplifier 224 is
configured to amplify the imaginary part 248 of the output complex
signal 234 to generate an amplification result. In some
embodiments, the amplifier is configured to amplify the imaginary
part of the output complex signal by an amplification gain. The
amplification gain may be fixed or programmable. The amplifier may
be implemented with one or more suitable digital circuits.
[0043] In the embodiment depicted in FIG. 2, the delay element 226
is configured to delay a rotation angle signal phi related to the
second input complex signal 232. For example, the delayed rotation
angle signal has a waveform that is identical to the waveform of
the rotation angle signal phi only delayed by a certain amount of
time. The delay element may be implemented with one or more
suitable digital circuits. For example, the delay element may be
implemented using one or more adjustable capacitors and/or one or
more variable resistors.
[0044] In the embodiment depicted in FIG. 2, the subtractor 228 is
configured to subtract the amplification result from the delayed
rotation angle signal to generate the rotation angle signal phi.
The subtractor may be implemented with one or more suitable digital
logic circuits.
[0045] In some embodiments, the complex multiplier 222 is
configured to rotate the incoming complex signal 230 by exp(j*phi),
where phi is the rotation angle signal that is controlled by the
phase rotation loop and j is complex unity. In these embodiments,
the output complex signal 234 of the complex multiplier can be
expressed as:
c_xout=(cos(phi(j))+1i*sin(phi(j)))*(i_data_d(j)+1i*q_data_d(j)),
(1)
where c_xout represents the output complex signal, phi represents
the rotation angle signal, cos represents the Cosine function, sin
represents the Sine function, i_data_d(j) represents the baseband
in-phase (I) component of the incoming complex signal, q_data_d(j)
represents the baseband quadrature (Q) component of the incoming
complex signal, i_data_d(j)+1i*q_data_d(j) represents the incoming
complex signal, cos(phi(j))+*sin(phi(j)) represents the second
input complex signal 232. The real part 246 of the output complex
signal can be expressed as:
i_xout(j)=real(c_xout) (2)
where c_xout represents the output complex signal, real represents
a real function that returns the real part of a given complex
number, and i_xout(j) presents the real part of the output complex
signal. The imaginary part 248 of the output complex signal can be
expressed as:
q_xout(j)=imag(c_xout) (3)
where c_xout represents the output complex signal, imag represents
an imaginary function that returns the imaginary part of a given
complex number, and q_xout(j) represents the imaginary part of the
output complex signal. The phase rotation loop starts with an
initial phase rotation angle signal phi and updates the phase
rotation angle signal phi dependent on a signal phe that is input
into the amplifier. The signal phe can be expressed as:
phe=q_xout(j) (4)
where q_xout(j) represents the imaginary part of the output complex
signal. The speed of phase rotation regulation is governed by the
amplification gain ag of the amplifier, which is also referred to
as the regulation constant. The amplification gain ag may be
constant or variable and reprogrammable. In some embodiments,
reference values for the complex multiplier are stored in a storage
device (e.g., memory) in order to minimize the implementation
complexity. The phase rotation angle signal phi can be expressed
as:
phi(j)=phi(j-1)-ag*phe (5)
where phi(j) represents the rotation angle signal and phi(j-1)
represents the delayed rotation angle signal, which is a delayed
version of the rotation angle signal.
[0046] Table 1 provides example operating parameters of the phase
rotator 220 depicted in FIG. 2 in an example operation of the phase
rotator. In the example operation, the baseband in-phase (I)
component, i_data_d(j), of the incoming complex signal 230 and the
baseband quadrature (Q) component, q_data_d(j), of the incoming
complex signal are both set to 100 and the amplification gain ag of
the amplifier 224 is set to 0.2. Initially, the value of rotation
angle signal, phi(j), is at 0. Based on equation (1), during a
first clock cycle, the complex multiplier 222 generates an output
complex signal 234 whose the real part i_xout(j) and the imaginary
part q_xout(j) are both at 100. At the end of the first clock
cycle, the value of rotation angle signal, phi(j), is updated to
0-0.2*100, which is -20 degrees, based on equation (5). During a
second clock cycle, because the rotation angle signal, phi(j), is
at -20 degrees, the complex multiplier generates an output complex
signal whose the real part i_xout(j) is around 128.17 and the
imaginary part q_xout(j) is around 59.77 based on equation (1). At
the end of the second clock cycle, the value of rotation angle
signal, phi(j), is updated to -20-0.2*59.77, which is around -31.95
degrees, based on equation (5). During a third clock cycle, because
the value of rotation angle signal, phi(j), is around -31.95
degrees, the complex multiplier generates an output complex signal
whose the real part i_xout(j) is around 137.77 and the imaginary
part q_xout(j) is around 31.92 based on equation (1). At the end of
the third clock cycle, the value of rotation angle signal, phi(j),
is updated to -31.95-0.2*31.92, which is around -38.34 degrees,
based on equation (5). During a fourth clock cycle, because the
value of rotation angle signal, phi(j), is around -38.34 degrees,
the complex multiplier generates an output complex signal whose the
real part i_xout(j) is around 140.47 and the imaginary part
q_xout(j) is around 16.41 based on equation (1). At the end of the
fourth clock cycle, the value of rotation angle signal, phi(j), is
updated to -38.34-0.2*16.41, which is around -41.62 degrees, based
on equation (5). During a fifth clock cycle, because the value of
rotation angle signal, phi(j), is around -41.62 degrees, the
complex multiplier generates an output complex signal whose the
real part i_xout(j) is around 141.18 and the imaginary part
q_xout(j) is around 8.34 based on equation (1). At the end of the
fifth clock cycle, the value of rotation angle signal, phi(j), is
updated to -41.62-0.2*8.34, which is around -43.29 degrees, based
on equation (5). During a sixth clock cycle, because the value of
rotation angle signal, phi(j), is around -43.29 degrees, the
complex multiplier generates an output complex signal whose the
real part i_xout(j) is around 141.36 and the imaginary part
q_xout(j) is around 4.23 based on equation (1). At the end of the
sixth clock cycle, the value of rotation angle signal, phi(j), is
updated to -43.29-0.2*4.23, which is around -44.13 degrees, based
on equation (5). During a seventh clock cycle, because the value of
rotation angle signal, phi(j), is around -44.13 degrees, the
complex multiplier generates an output complex signal whose the
real part i_xout(j) is around 141.41 and the imaginary part
q_xout(j) is around 2.14 based on equation (1). At the end of the
seventh clock cycle, the value of rotation angle signal, phi(j), is
updated to -44.13-0.2*2.14, which is around -44.56 degrees, based
on equation (5). During an eighth clock cycle, because the value of
rotation angle signal, phi(j), is around -44.56 degrees, the
complex multiplier generates an output complex signal whose the
real part i_xout(j) is around 141.42 and the imaginary part
q_xout(j) is around 1.08 based on equation (1). Therefore, the
imaginary part 248 of the output complex signal 234 is reduced in
each clock cycle such that encoded information is predominantly
carried by the real part 246 of the output complex signal. Because
the information is predominantly carried by the real part of the
output complex signal, information can be decoded from the real
part of the output complex signal by a digital signal processor
(e.g., using decoding and bit-slicing operations to form the
logical representations of true and false), thereby reducing or
even eliminating the need to decode the imaginary part of the
output complex signal to recover the carried information.
Consequently, a separate decoder is not needed to decode the
imaginary part of the output complex signal. Additionally, a
separate/parallel decoding and bit-slicing chain is not needed
within a digital decoder to decode the real part of the output
complex signal. At the end of the eighth clock cycle, the value of
rotation angle signal, phi(j), is updated to -44.56-0.2*1.08, which
is around -44.78 degrees, based on equation (5).
TABLE-US-00001 TABLE 1 Clock Cycle IQ data phi (degrees) cos(phi)
sin(phi) real imaginary 1 100 0 1 0 100 100 2 100 -20.00 0.94 0.34
128.17 59.77 3 100 -31.95 0.85 -0.53 137.77 31.92 4 100 -38.34 0.78
-0.62 140.47 16.41 5 100 -41.62 0.75 -0.66 141.18 8.34 6 100 -43.29
0.73 -0.69 141.36 4.23 7 100 -44.13 -0.72 0.70 141.41 2.14 8 100
-44.56 0.71 -0.70 141.42 1.08
[0047] FIG. 3 is a plot of the real part 246 and the imaginary part
248 of the output complex signal of the complex multiplier 234 as
depicted in FIG. 2 and the rotation angle signal phi in an example
operation of the phase rotator 220. In the plot depicted in FIG. 3,
a curve 370 represents the real part of the output complex signal,
a curve 380 represents the imaginary part of the output complex
signal, and a curve 390 represents the rotation angle signal phi.
As shown in FIG. 3, the imaginary part of the output complex signal
and the rotation angle signal phi decreases during each clock cycle
while the real part of the output complex signal increases during
each clock cycle. Therefore, encoded information is predominantly
carried by the real part of the output complex signal.
Consequently, information can be decoded from the real part of the
output complex signal by a digital signal processor (e.g., using
decoding and bit-slicing operations to form the logical
representations of true and false).
[0048] FIG. 4 depicts a receiver unit 414 that is an embodiment of
the RF transceiver 114 of the communications device 102 and/or the
RF transceiver 124 of the counterpart communications device 104
depicted in FIG. 1. The difference between the receiver unit 414
depicted in FIG. 4 and the receiver unit 214 depicted in FIG. 2 is
that the receiver unit 414 depicted in FIG. 4 further includes a
baseband IQ demodulator 450 configured to generate complex inputs
for the phase rotator 220 and a decoder 460 configured to decode
outputs of the phase rotator. Specifically, in the embodiment
depicted in FIG. 4, the receiver unit includes the baseband IQ
demodulator, which includes a clock source 452, separate Q and I
mixers 454-1, 454-2, a low pass filter (LPF) unit 456, and an
analog-to-digital converter (ADC) unit 458, the phase rotator 220,
which includes the complex multiplier 222, the amplifier 224, the
delay element 226, and the subtractor 228, and the decoder 460. The
receiver unit depicted in FIG. 4 is a possible implementation of
the RF transceiver 114 or 124 depicted in FIG. 1. However, the RF
transceiver 114 or 124 depicted in FIG. 1 can be implemented
differently from the receiver unit depicted in FIG. 4. For example,
in some embodiments, the receiver unit includes a digital phase
locked loop (DPLL), which in turn includes a clock recovery unit
and a loop filter. In another example, although the decoder is a
component of the receiver unit in the embodiment depicted in FIG.
4, in other embodiments, the decoder is not part of the receiver
unit.
[0049] In the embodiment depicted in FIG. 4, the baseband IQ
demodulator 450 is configured to generate complex inputs for the
phase rotator 220 based on an RF input signal 448. In some
embodiments, the RF input signal is received from the antenna 112
or the antenna 122. The baseband IQ demodulator may be implemented
with one or more suitable analog or digital circuits. The clock
source 452 is configured to generate clock signals for the mixers
454-1, 454-2. In some embodiments, the clock source is implemented
as an oscillator. The baseband IQ demodulator can generate the
baseband in-phase (I) and quadrature (Q) components based on the RF
input signal and the clock signals. The separate I and Q mixers are
configured to mix the clock signals with the RF signal. The LPF
unit 456 is configured to filter higher frequency signal components
of output signals from the mixers. The ADC unit 458 is configured
to convert one or more analog signals from the LPF unit into
digital I/Q data, which is input into the phase rotator. In an
example operation of the baseband IQ demodulator, the RF input
signal from a receiver antenna is mixed with a local clock signal
at the separate I and Q mixers. The mixer outputs are low-pass
filtered and converted into digital I/Q signals, which are output
to the complex multiplier.
[0050] Compared to a receiver that relies on a recovered clock for
data reception, the receiver unit 414 depicted in FIG. 4 does not
rely solely on a clock-recovery mechanism for data reception and
decoding. For example, the phase rotator operates with the local
clock source 452 (e.g., a local oscillator) of the baseband IQ
demodulator 450 to implement data reception and decoding. Because
the receiver unit depicted in FIG. 4 does not rely solely on a
clock-recovery mechanism for data reception and decoding, parasitic
phase modulation that may be introduced based on the proximity
between the communications devices does not affect data reception
and decoding at the corresponding receiver unit.
[0051] In the embodiment depicted in FIG. 4, the decoder 460 is
configured to decode the real part 246 of the output complex signal
234 of the phase rotator 220 into decoded bits. The decoder may be
implemented as hardware, software, firmware, and/or a combination
of hardware, software, and/or firmware. In some embodiments, the
decoder is implemented with one or more suitable digital logic
circuits. In an embodiment, the decoder is implemented as a
processor such as a microcontroller or a CPU.
[0052] FIG. 5 is a process flow diagram of a method for operating a
communications device in accordance with another embodiment of the
invention. At block 502, a first input complex signal is multiplied
with a second input complex signal to generate an output complex
signal. At block 504, an imaginary part of the output complex
signal is amplified to generate an amplification result. At block
506, a rotation angle signal that is related to the second input
complex signal is delayed. At block 508, the amplification result
is subtracted from the delayed rotation angle signal to generate
the rotation angle signal. The communications device may be the
same or similar to the communications devices described above with
respect to FIGS. 1-4.
[0053] Although the operations of the method(s) herein are shown
and described in a particular order, the order of the operations of
each method may be altered so that certain operations may be
performed in an inverse order or so that certain operations may be
performed, at least in part, concurrently with other operations. In
another embodiment, instructions or sub-operations of distinct
operations may be implemented in an intermittent and/or alternating
manner.
[0054] It should also be noted that at least some of the operations
for the methods may be implemented using software instructions
stored on a computer useable storage medium for execution by a
computer. As an example, an embodiment of a computer program
product includes a computer useable storage medium to store a
computer readable program that, when executed on a computer, causes
the computer to perform operations, as described herein.
[0055] The computer-useable or computer-readable medium can be an
electronic, magnetic, optical, electromagnetic, infrared, or
semiconductor system (or apparatus or device), or a propagation
medium. Examples of a computer-readable medium include a
semiconductor or solid-state memory, magnetic tape, a removable
computer diskette, a random-access memory (RAM), a read-only memory
(ROM), a rigid magnetic disc, and an optical disc. Current examples
of optical discs include a compact disc with read only memory
(CDROM), a compact disc with read/write (CD-R/W), a digital video
disc (DVD), and a Blu-ray disc.
[0056] In the above description, specific details of various
embodiments are provided. However, some embodiments may be
practiced with less than all of these specific details. In other
instances, certain methods, procedures, components, structures,
and/or functions are described in no more detail than to enable the
various embodiments of the invention, for the sake of brevity and
clarity.
[0057] Although specific embodiments of the invention have been
described and illustrated, the invention is not to be limited to
the specific forms or arrangements of parts so described and
illustrated. The scope of the invention is to be defined by the
claims appended hereto and their equivalents.
* * * * *